The present invention relates to rotary kilns, and more particularly to a lump breaking system for use at the discharge end of a rotary kiln to reduce the size of large particles prior to discharge. The device restricts the discharge of oversized agglomerations of processed material from the rotary kiln and reduces the size of the agglomerations to an acceptable size prior to discharge of the processed materials from the kiln.
A conventional rotary kiln includes a simple cylinder or shell installed at an incline. Raw material feed to be pyroprocessed is charged into the kiln from an inlet at the elevated end, and thereafter the feed material is typically calcinated by applying heat while the cylinder is rotated, and the calcinated product is discharged from an outlet at the exit or lower end of the kiln. Kilns of this type are well known in the art and are capable of treating raw materials of many different kinds and at a wide variety of particle sizes and shapes.
The hot pyroprocessed material exiting from the kiln is then typically cooled before further processing. Many different types of arrangements have been developed for cooling such material. When passing from the kiln to the cooling phase, a preferred maximum size of the product particles is desirable.
During typical operation, agglomerated “dust balls” often form within the kiln. An agglomerated dust ball must be broken up prior to discharge from the rotary kiln. Presently, various methods are known for breaking the dust balls into smaller sizes prior to discharge for further processing.
One example of a device for reducing the size of dust balls within a rotary kiln is shown and described in U.S. Pat. No. 6,474,985 entitled “Toothed Grate for Rotary Kiln Peripheral Discharge Opening”. This device is particularly desirable for use on kilns with a peripheral discharge, typically into satellite or tube coolers. The device shown in the '985 patent includes a raised grate that fits within the peripheral openings in the kiln shell leading to the satellite or tube coolers. The raised grate has teeth formed on the device that break up the dust balls as they make contact with the grate during rotation of the kiln. The raised grate works in combination with a raised damn at the discharge end of the rotary kiln to prevent large particles from being discharged from the rotary kiln.
A second type of device for reducing the size of dust balls prior to discharge from a rotary kiln includes a series of one part castings that mount to the periphery of the discharge end of a refractory lined rotary kiln. The casting is typically bolted to the kiln shell, with the lower portion of the casting embedded in the refractory liner of the kiln. The casting includes multiple flat web portions that are perpendicular to the kiln axis and project above the refractory to act as a dust ball lump breaker. Although this type of system functions well to break the dust balls into a more manageable size, when the lump breaker portion of the design becomes worn or eroded after a period of use and needs replacement, the embedding refractory, mounting bolts and the entire casting must be removed and replaced.
It is thus desirable to provide an arrangement and system at the discharge end of a rotary kiln to break agglomerated dust balls into particles having reduced size that allows the operating components of the system to be easily removed and replaced without removing the refractory lining of the rotary kiln. It is additionally desirable to provide such a system that provides multiple sections such that worn portions of the system can be removed without requiring replacement of the entire system.